Routing devices within a network, often referred to as routers, maintain tables of routing information that describe available routes through the network. Upon receiving a packet, a router examines information within the packet and forwards the packet in accordance with the routing information. In order to maintain an accurate representation of the network, routers exchange routing information in accordance with one or more routing protocols, such as an interior gateway protocol (IGP) or Border Gateway Protocol (BGP).
The term “link” is often used to refer to the connection between two devices on a network. The link may be a physical connection such as a copper wire, a coaxial cable, any of a host of different fibre optic lines or a wireless connection. In addition, network devices may define “virtual” or “logical” links, and map the virtual links to the physical links. In other words, the use of virtual links provides a degree of abstraction. As networks grow in size and complexity, the traffic on any given link may approach a maximum bandwidth capacity for the link, thereby leading to congestion and loss.